Radio apparatus



Patented Dec. 8, 1931 WARREN E. DANLE'I, OF HIGHLAND PARK, ILLINOIS RADIO APPARATUS Application filed March 25, 1926. Serial No. 97,273.

'My invention relates to radio apparatus and moreparticularly to a synchronized or single control audion tube receiver.

The invention is chiefly characterized by,

having each pair of coupled amplifying circuits balanced in natural frequency with the couple formed by the aerial circuit and "the first stage circuit, and means for simultaneous ly and similarly tuning the ampllfying circuits.

Heretofore in 'multi-stage audion tube radio apparatus, the tuning elements of the several stages have been simultaneously adjusted under one control, but it has been found that, to maintain resonance 1n all stages, the tuning of the different stages must be slightly varied as the frequency settings are varied, especially the tuning of the circuit which is immediately coupled to the aerial. It is well known that the resonance characteristics of any circuit are changed when that circuit is coupled with another circuit; and that when two circuits are coupled together the effect of a certain amount of tuning of either is modified. In cascade stages of amplification, all the circuits are commonly physical equivalents, except of course, the aerial circuit; and the inter-reactions are, therefore, all the same except between the aerial circuit and the circuit coupled therewith. It is then apparent that by balancing the inter-reaction of the coupling between the aerial and the first stage in the remaining couplings, as is characteristic of the present invention, that the several stages may be similarly tuned under one control and a condition of perfectly uniform resonance maintained. It is thought that the syntonization of the various similar circuits is more important in selective tuning than a critical ad ustment of the various couplings, provided the latter are fairly loose. Further it is thought that slight variations in the values of the couplings can be compensated by corrective variations of the tuning of the respective primaries of the coupled circuits.

Illustrative embodiments of this invention are shown in the accompanying drawlngs, in

which Figure 1 is a circuit diagram of a two-tube V i receiving apparatus.

Fig. 2 illustrates a multiple stage apparatus.

In the drawings, the primary coil 1 of the transformer or coupler 2 is included in the clrcuit of the aerial 3. The secondary 4 of the transformer 2 is connected in the resonating grid circuit 5, between the grid 6 of the audion tube 7 and the filament 8. A variable condenser 9 is shunted across the-coil 4.-

The amplifying or plate circuit 10 is connected from the plate 11, of the tube 7, through the primary coil 12 of the first stage transformer 13, through the B battery and back to the filament 8. The secondary 14 of the transformer 13 is included in the second resonating or grid circuit 15 which connects from the grid 16 of the detector tube 17 through the condenser 18, through the coil 14 and finally back to the filament 19 of the tube 17. The variable condenser 20 is shunted across the coil 14, and the grid leak 21 is shown betwen the grid 16 and the filament 19. a

The plate 22 of the tube 17 is connected to the phones 23, B battery and back to the filament.

For balancing or syntonizing the primaries of coupler 2 and coupler 13, a condenser 24 is shown connected across the coil 12.. The capacity of condenser 24 is adjusted to make the Figure 2 is a skeletonized diagram illus- I trating the use of additional stages of radio amplification.- In this diagram details of the wiring of the battery circuits are omitted, for simplicity, and reference characters 25, 26 and 27 designate the several stages, not merely the tubes thereof. The transformer 2 couples the first stage 25 with the aerial 3. The second stage 26 is coupled to the first stage 25 by means of the transformer 13, and

the third stage 27 is coupled to 26 by means of the trans ormer 13.1. The condensers 24 are shown connected across the primaries of the transformers 13 and 13.1 to balance the respective stages with the aerial circuit, in the same manner as in Figure 1. The similar condensers 9, and 20.1 are connected as usual across the similar secondaries of the transformers 2, 13 and 13.1

In actual construction, the variable condensers 9 and 20 in Figure 1, or 9, 20 and 20.1 in Figure 2, are mounted to be simultaneously controlled, by a common shaft or otherwise. In the drawings, a crank and lever connection 28 is shown diagrammatically between the shafts of the variable condensers.

In operation, the primary circuits of couplers 2, 13 and 13.1 are tuned as described above, to approximately the same frequency. This need be done only'once for any given aerial, and indeed condensers 24 may be fixed condensers chosen to fairly well fit the case of the average aerial. The variable condensers 9, 20, 21.1, arethereafter operated to tune their respective secondary circuits to a desired signal frequency, a single tuning control sufficing to give substantially perfect resonance in all the stages since the matching of the primary circuits of all the stages results in producing substantially the same coupled circuit effects in all the said stages. When a wave of the desired frequency is impressed on the aerial circuit, the energy is communicated and amplified through the remaining circuits. Since substantially perfect resonance is maintained-for all adjustments, the tuning is extremely selective and sensitive.

While illustrative embodiments of my invention have been herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention.

I claim:

1. In a vacuum tube radio apparatus an aerial circuit, a grid circuit coupled to the aerial circuit, a variable condenser shunted across the grid circuit, a plate circuit coupled with the grid circuit, a second grid circuit coupled tothe plate circuit, a variable condenser shunted across said second grid circuit, means for giving to the plate circuit substantially the same characteristics as exist in the aerial circuit, the coupling between the first plate circuit and the second grid circuit being adjusted to the coupling'between the aerial circuit and the first grid circuit, so that the apparatus may be tuned by moving both of said condenserssimultaneous'ly and equally.

2. In a radio apparatus having vacuum tubes, an aerial circuit, one tube having a grid circuit coupled to the aerial circuit, the plate circuit of said tube controlling the grid circuit of a subsequent tube, an oscillating circuit coupled to said second named id circuit, the coeflicients of coupling of eaci of said pairs of coupled circuits being ap roximate y identical, means for giving substantially the same fixed frequency characteristic to both the said oscillating circuit and the aerial circuit.

3. In a radio apparatus having vacuum tubes, a plurality of pairs of coupled resonant amplifying circuits cooperating with said tubes one pair including an aerial circuit and the other pairs in cascade therewith, the coefiicient of coupling of each of said pairs being substantially the same, one, circuit of each pair being provided with means for tuning it to a desired signal frequency, means for giving to eachof the remaining circuits of said pairs a substantially identical fixed frequency characteristic.

4. The combination, in a radio receiving apparatus, of two or more fixed-tune resonating circuits, said fixed-tune resonating circuits being tuned to substantially the same frequency,two or more variable-tune resonating circuits,said variable-tune resonating circuits and said fixed-tune resonating circuits being coupled together, to substantially the same extent, in pairs, and a single means for simultaneously varying the electrical periods of said variable-tune resonating circuits.

5. The combination, in a radio receiving apparatus having an antenna circuit, of two fixed-tune resonatin circuits, said fixed-tune resonating circuits eing tuned to substantially the same frequency, two variable-tune resonating circuits, said variable tune resonatingcircuits and said fixed-tune resonating circuits being coupled together, to substantially the same extent, in pairs, and a single means for simultaneousl varying the electrical periods of said varia le-tune resonating circuits.

6. .The combination, in a radio receiving apparatus comprising a receiving circuit, of two fixed;tune circuits comprising inductances and capacitances and having substantially the same resonant frequencies, two variable-tune circuits comprising inductances and capacitances and having substantially the same range of resonant frequencies, said fixed-tune circuits being coupled to said variable-tune circuits, to substantially the same .extent, in two pairs, each of said airs comprising one of said fixed-tune circuits and one of said variable-tune circuits, and a single means for simultaneously varying the electrical periods of said variable-tune circuits.

Signed at Chicago this 22nd day of March, 1926.

WARREN E. DANLEY. 

